As an active non-metallic material, iodine was first discovered by the French chemist Courtois, B. (1777-1838) in 1811, and has shown its important application values in various fields. Used as a medical disinfectant and agricultural germicide, iodine plays an important role in the disinfection and sterilization in the form of I2 and HOI.
Studies have shown that iodine reacts with pathogens in various ways. Iodine interacts with hydroxyl-, amino-, hydrocarbyl-, and mercapto-groups to affect the survival of microorganisms. After alkaline amino acids (lysine, histidine and arginine) and nucleotide bases (adenine, cytosine and guanine) forming iodine derivatives, their important hydrogen bonds are destroyed and blocked, which causes fatal changes to the corresponding proteins, enzymes and nucleic acids. After a mercapto-group of cysteine is oxidized by iodine, its ability to form disulfide bond loses and protein synthesis is blocked. Cell respiration enzymes lose its activity after its mercapto groups are destroyed. Phenolic groups of tyrosine react with iodine to form monoiodide or diiodide derivatives, and the iodine atoms at ortho position will prevent functions of phenolic hydroxyl groups due to steric hindrance and electronic effect. Iodine can also alter the physical properties and chemical properties of unsaturated fatty acids by destroying carbon-carbon double bonds in its molecules, resulting in irreversible strong bactericidal properties. However, due to iodine's volatility and light instability, its durable effect is poor and efficacy cannot be maintained for a long term, which has largely restricted its use in disinfection and pesticide.
Since its discovery, iodine, as a disinfectant, has experienced 3 generations of developing stages as iodine tincture, iodophor and PVP-I, in the 1980s, the German patents for invention DE-2941387 and DE-3060935 provided polyvinyl pyrrolidone (PVP-I), which is widely recognized and used in the worldwide medical treatment and public health fields. However, due to high cost and effect restrictions, it is not widely used as agricultural disinfectant and germicide. Disclosure in Patents “amino acid complex iodine” (CN1207271C) and iodine oligosaccharide acids (ZL201010288868.8) has extended the application of complex iodine in the fields of agricultural disinfectant (aquaculture disinfectant) and agricultural germicide (control agents for plant virus disease and bacterial disease). The defects in terms of the complex's structural stability and its conductivity and high potency in the plant restrict its application. To stabilize iodine molecules, some stable complex carrier was chosen to prepare stable complex iodine. But temperature required for maintaining complex iodine's stability is basically under 80 C. Instability is still a problem when the complex iodine was put under light condition, which is the biggest obstacle that blocks its application as agricultural germicide. Moreover, in above said complex iodine, to stabilize iodine molecules, a large ratio of complexing carriers is required. This will result in a high product cost and affect efficient function exertion of iodine, weakening its activity.
Until now, iodine disinfectant/germicide product especially suitable for agricultural filed or related literature/report about developing iodine disinfectant/germicide suitable for agricultural filed have not been seen, let alone iodine disinfectant/germicide which can cure and well control specific parasitism disease of plant causing widespread disease in agricultural field, such as Citrus Huanglongbing (HLB or citrus greening disease) and citrus bacterial canker disease, plant virus disease and vascular bundle disease.